Clinical features: eruptive xanthoma, recurrent pancreatitis, and lipemia retinalis.
LPL (lipoprotein lipase) activity is low.
LPL Activity Estimation
Post-heparinized blood samples are used because heparin in circulation competes with heparan sulfate on vessel walls, causing enzymes to detach from the vessel wall and attach to circulating heparin. If LPL activity is low in post-heparinized individuals: Apo C II defect or an LPL defect. Mixing study: To differentiate Apo C defect from LPL defect.
To post heparinized plasma from patients, add an equal amount of pooled normal plasma which acts as a source of apo C II.
Following mixing, if LPL activity normalizes: apo C II defect and it responds to FFP administration.
Following mixing, if LPL activity does not normalize: LPL defect.
AKA Apo E defect/remnant disease/broad beta disease and familial dysbetalipoproteinemia.
Remnant lipoproteins are not cleared of circulation. ·
Elevation of both cholesterol and TGL *caused by a homozygous E2 mutation.
Lipoprotein Electrophoresis
Glass slide with support medium (Agarose)
↓
On one end of a glass slide serumlipoprotein applied by micropipette
↓
Glass slide is placed in electrophoretic tank, filled alkaline buffer
(pH - 8.3) - gives a negative charge to lipoprotein.
↓
To the point of application, a negatively charged electrode is connected and to
opposite point to positively charged electrode
↓
Lipoproteins move towards the oppositely charged electrode on
passing electric current
Migration is affected by
No. of negative charges that they carry
Size (larger particles will not be able to move) alpha
band or HDL: moves farthest because it has ↑ phospholipid, ↑ protein content, and more negative charges.
Chylomicron band: moves closest because of its huge size.
In a lipoproteinelectrophoresisfasting sample is taken, normally, a chylomicron band will not be present because it is a product of dietary triacylglycerol
Dietary fat is never a cause of fatty liver, as it gets absorbed as chylomicrons, which never reach the liver but rather extrahepatic tissues.
Excessive peripheral lipolysis: Hormone-sensitive lipase cleaves triacylglycerol present in adipose tissue → glycerol and fatty acids →liver (for oxidation of fatty acids); excessive fatty acids reaching the liver cause fatty liver.
Anything stimulating hormone-sensitive lipase can cause fatty liver.
Hormone-sensitive lipase is inhibited by insulin.
Conditions with low insulin levels (such as diabetes mellitus and starvation) can lead to fatty liver changes by causing excessive peripheral lipolysis.
Increased synthesis of lipid within the liver: anabolism—obesity and alcoholism.
Inhibits phosphatidylcholine synthesis, disrupting the organization of outeramphipathic layer.Impairs VLDLlipoprotein synthesis, preventing fat release from the liver.
Essential fatty acid deficiency
Prevents the formation of the inner non-polar lipid core, leading to fatty liver changes.
Ccl4 (Carbon Tetrachloride) toxicity
Disrupts ribosomes from the endoplasmic reticulum, causing damage and preventing apoprotein synthesis, resulting in fatty liver changes.
Alcohol consumption
Causes oxidative stress leading to lipidperoxidation of the endoplasmic reticulum membrane, impairing apoproteinsynthesis and causing fatty liver changes.
Orotic aciduria
Damages Golgi bodies, contributing to the development of fatty liver changes.
Important Points to Remember
The hyperlipoproteinemia, which presents with only an elevation of cholesterol: Type Iia.
Puromycin: protein synthesisinhibition so Apo proteins are not synthesized, which causes fatty liver changes.
The hyperlipoproteinemias, which present with only an elevation of triglycerides: Type I, Type IV , Type V
Lipoprotein X is a feature of obstructed jaundice and LCAT deficiency.
A broad beta band in lipoproteinelectrophoresis is a feature of Apo E defect.
Q. A 15 year old child presents with repeated episodes of pancreatitis. Serumtriglyceride concentration is 1100 mg/dL, Cholesterol is 250 mg/dL. Lipoproteinlipase activity is low. The diagnosis is:
Type I Hyperlipoproteinemia
Type IIa Hyperlipoproteinemia
Type III Hyperlipoproteinemia
Type IV Hyperlipoproteinemia
Q. A patient presents with corneal haziness, high urea, high creatinine, high potassium. Suspecting LCAT deficiency, Lipoproteinelectrophoresis was performed. His HDL was undetectable. Name the abnormallipid found in the electrophoresis?
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